How do you calculate rejection rate?

Divide rejected parts by parts inspected and multiply by 100. For 15 rejects out of 750 inspected, that is 15 ÷ 750 × 100 = 2% rejected.

What is a good rejection rate in manufacturing?

It depends on the process and tolerance class, but many machining and assembly shops target under 1-2%. In the example the rate is 2% against a 1% target, so it is 1 point over goal and worth investigating.

What is the difference between rejection rate and scrap rate?

Rejection rate counts every part that fails inspection, including those that can be reworked. Scrap rate counts only parts that are unrecoverable and thrown away, so scrap rate is usually lower.

How is rejection rate different from first-pass yield?

First-pass yield is the share of parts that pass with no rework; rejection rate is essentially its complement on inspected units. A 2% rejection rate roughly implies a 98% pass rate on that inspection point.

Does a low rejection rate always mean good quality?

Not necessarily. If inspection coverage is low or gauging is loose, defects escape to the customer while the internal rejection rate looks healthy. Pair it with PPM returns and audit results.

How many parts should I inspect to trust the rate?

Enough that a single reject does not swing the number wildly. At 750 inspected, one part equals about 0.13 points; at 50 inspected, one part equals 2 points, so small samples are noisy.

Quality & Metrology calculator

Rejection Rate Calculator

Rejection rate is the percentage of inspected parts that fail acceptance criteria and are scrapped or reworked. Quality engineers, incoming inspection teams, and production supervisors track it per lot, per shift, and per part number to catch process drift before it eats margin. A rising rejection rate is often the first quantitative signal of a worn tool, a bad material heat, or an out-of-spec setup. Unlike scrap cost, it normalizes across batch sizes so you can compare a 200-piece run to a 5,000-piece run fairly.

What this calculator does

Calculate a rejection rate from rejected parts and parts inspected, and compare it against your target rejection rate.
Use it to track reject levels on a quality board and to trigger containment or corrective action when the target is missed.
It computes the share of inspected parts that were rejected and the gap in points between that rate and your target.

Formula used

Rejection rate = rejected parts ÷ parts inspected × 100
Gap to target = rejection rate - target rejection rate

Inputs explained

Rejected parts:
Parts inspected:
Target rejection rate:

How to use the result

Use it at incoming inspection, after each production run, or during a containment to quantify how far a lot sits from your acceptance goal.
It only reflects the sample actually inspected — if inspection coverage is partial or the sample is not random, the rate understates or misrepresents true defective rate in the population.

Current U.S. benchmarks

U.S. manufacturing runs at 75.6% of capacity (Federal Reserve, May 2026). New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate rejection rate? Divide rejected parts by parts inspected and multiply by 100. For 15 rejects out of 750 inspected, that is 15 ÷ 750 × 100 = 2% rejected.
What is a good rejection rate in manufacturing? It depends on the process and tolerance class, but many machining and assembly shops target under 1-2%. In the example the rate is 2% against a 1% target, so it is 1 point over goal and worth investigating.
What is the difference between rejection rate and scrap rate? Rejection rate counts every part that fails inspection, including those that can be reworked. Scrap rate counts only parts that are unrecoverable and thrown away, so scrap rate is usually lower.
How is rejection rate different from first-pass yield? First-pass yield is the share of parts that pass with no rework; rejection rate is essentially its complement on inspected units. A 2% rejection rate roughly implies a 98% pass rate on that inspection point.
Does a low rejection rate always mean good quality? Not necessarily. If inspection coverage is low or gauging is loose, defects escape to the customer while the internal rejection rate looks healthy. Pair it with PPM returns and audit results.

Last reviewed 2026-05-12.